Boat propeller

ABSTRACT

A boat propeller includes a gear box, an impeller, a stream-guiding ring, and a stream-shaping nozzle. The gear box has a casing and a transmission shaft partially received in the casing. The impeller has an impeller shaft and vanes. The impeller shaft has a hollow columnar outer shaft housing and a hollow columnar inner shaft housing. The inner and outer shaft housings are connected using a plurality of rib portions. The inner shaft housing is further connected to the transmission shaft of the gear box. The vanes are integrated formed on an outer peripheral surface of the outer shaft. The stream-guiding ring is assembled to the casing of the gear box to house the impeller. The stream-shaping nozzle is connected to a rear end of the stream-guiding ring for providing stream-shaping effects. Thereby, the boat propeller has its water inlet diameter maximized, which helps to improve propulsive efficiency.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to boat propellers, and more particularlyto a boat propeller that helps to improve propulsive efficiency.

2. Description of the Related Art

The existing boat propellers structurally have an outer shaft housing,an inner shaft housing, and a plurality of blades. The inner shafthousing is received in the outer shaft and is connected to the innerperipheral surface of the outer shaft through a plurality of ribportions. Each of the blades is integratedly connected to the outerperipheral surface of the outer shaft. When the propeller is driven byan engine to operate at high speed, the blades push water streamsbackward and the counter force generated thereby can work for propulsionof the boat.

To further enhance propulsion, a known approach is to such design theouter shaft housing that it has a changing cross-sectional area, whichbecomes smaller as the outer shaft housing extends backward. This helpsto accelerate water streams flowing therethrough, and to in turnincrease the counter force acting on the boat. However, in practicaluse, since the outer shaft housing is tapered in shape and the spacearound the propeller tends to be restricted due to boat design and otherfactors, the blades are consequently limited in terms of dimensionalparameter (such as the rake, the pitch and more). This hinders theblades from effectively compressing water streams, leading tocompromised propulsive efficiency.

SUMMARY OF THE INVENTION

The primary objective of the present invention is to provide a boatpropeller that has improved propulsive efficiency.

To achieve the foregoing objective, the disclosed propeller comprises agear box, an impeller, a stream-guiding ring, and a stream-shapingnozzle. The gear box includes a casing and a transmission shaft. Thetransmission shaft is rotatably installed in the casing, and thetransmission shaft has its front end received in the casing so that itsrear end juts out the casing. The impeller has an impeller shaft thatincludes an outer shaft housing and a hollow inner shaft housing, bothbeing hollow columnar. The inner shaft housing is received in the outershaft housing and is connected to the outer shaft housing through aplurality of rib portions, while being coaxially connected to thetransmission shaft of the gear box, so that the impeller is driven bythe transmission shaft of the gear box to rotate. In addition, theimpeller further has a plurality of vanes that are integratedly formedon the outer peripheral surface of the outer shaft. The stream-guidingring is assembled to the casing of the gear box and houses the impeller,so that the impeller rotating draws water streams into thestream-guiding ring. The stream-shaping nozzle is connected to the rearend of the stream-guiding ring, for shaping the water stream drawn intothe stream-guiding ring.

With the foregoing configuration, the disclosed propeller has its waterinlet diameter maximized, thereby improving propulsive efficiency. Inaddition, with the protection provided by the stream-guiding ring, theimpeller is unlikely to harm fishes, swimmers or divers around thebottom of the boat. This allows a boat having a shallow draft safe to beused. Even if the impeller is not fully immersed in water, propulsioncan still be provided desirably.

Preferably, the stream-shaping nozzle has a ring portion, a hollow axialportion, and a plurality of stream-shaping portions. The ring portion isconnected to the rear end of the stream-guiding ring. The hollow axialportion is defined in the ring portion and coaxially connected to theouter shaft housing of the impeller shaft of the impeller. Thestream-shaping portions are connected between the ring portion and thehollow axial portion and arranged equidistantly to circle the hollowaxial portion. The stream-shaping nozzle uses the stream-shapingportions to shape the water stream excited by the impeller into linearejections, thereby facilitating boat propulsion.

Preferably, the casing of the gear box has a tapered shaft. The taperedshaft and the impeller shaft of the impeller do not contact each other.Instead, an exhaust channel is left therebetween. Thereby, when the boatmoves backward, the exhaust gas generated by the engine can escapethrough the exhaust channel and will not interfere with water streams tocause turbulence.

Preferably, the inner shaft housing of the impeller is indirectlyconnected to the transmission shaft of the gear box through a bushing.The bushing has a shock-absorbing layer and a metal layer wrapping theshock-absorbing layer. In the event that a foreign object comes to theimpeller during operation, the shock-absorbing layer serves to absorbimpact and prevent the metal layer from burst while protecting thetransmission shaft from damage.

The detailed structure, features, assembly and/or use of the boatpropeller of the present invention will be explained in detail referredto the following Detailed Description. However, one skilled in the artshall understand that the detailed description and the specificembodiments in which the invention can be practiced are onlyillustrative and in no way form limitations to the scope of the presentinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a boat propeller of the presentinvention.

FIG. 2 is an exploded view of the boat propeller of the presentinvention.

FIG. 3 is a point view of an impeller in the boat propeller of thepresent invention.

FIG. 4 is a side view of the boat propeller of the present invention.

FIG. 5 is a rear view of the boat propeller of the present invention.

FIG. 6 is a partial cross-sectional view of the boat propeller of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

It is to be stated at first that in the disclosure, including theembodiments to be described below and the appended claims, all thedirectional terms are based on the orientations of them in the drawings.Besides, in the embodiments to be described below and the accompanyingdrawings, like numerals may refer to identical or similar components orstructural features.

Referring to FIG. 1 and FIG. 2, according to the present invention, aboat propeller 10 comprises a gear box 20, an impeller 30, astream-guiding ring 50, and a stream-shaping nozzle 60.

The gear box 20 is provided with a casing 21. The casing 21 has atapered shaft 22, an upper wing 23, a lower wing 24, a connectingportion 25 and an anti-swirl baffle 26. The tapered shaft 22 has achanging cross-sectional area that becomes larger as it extendsbackward. The upper wing 23 and the lower wing 24 are integratedlyconnected to top and bottom sides of the tapered shaft 22, respectively.The connecting portion 25 is integratedly connected to the top of theupper wing 23 and is configured to engage with an engine housing, whichis known in the art and not shown herein. The anti-swirl baffle 26integratedly is connected between the upper wing 23 and the connectingportion 25. In addition to a gear reduction unit that is known in theart and not shown herein, the gear box 20 further has a transmissionshaft 27. The gear reduction unit is installed in the casing 21, and isconfigured to connect a driving shaft of an engine, both known in theart and not shown herein. The transmission shaft 27 has its front endreceived in the tapered shaft 22 of the casing 21 and connected to thegear reduction unit. The transmission shaft 27 has its rear end juttingout the casing 21 provided with a toothed portion 28. With the foregoingconfiguration, the power generated by the engine is transmitted to thegear reduction unit through the driving shaft and then delivered to thetransmission shaft 27 after deceleration caused by the gear reductionunit, thereby rotating the transmission shaft 27.

The impeller 30 has an impeller shaft 31 and four vanes 38. As shown inFIG. 3, the impeller shaft 31 has a hollow columnar outer shaft housing32 and a hollow columnar inner shaft housing 33. The inner shaft housing33 is coaxially received in the outer shaft housing 32 and is connectedto the outer shaft housing 32 through four rib portions 37. The vanes 38are integratedly connected to the outer peripheral surface of the outershaft housing 32. Additionally, the outer shaft housing 32 has anengaging flange 34 integratedly extending outward from its rear end (asshown in FIG. 6), and the inner shaft housing 33 has a retaining flange35 and four positioning recesses 36 formed on the inner peripheralsurface in front of the retaining flange 35 (as shown in FIG. 3 and FIG.6).

Now referring to FIG. 2 and FIG. 6, the impeller 30 is indirectlyconnected to the transmission shaft 27 of the gear box 20 through abushing 40. The bushing 40 has a shock-absorbing layer 41 and a metallayer 43 wrapping the shock-absorbing layer 41. The shock-absorbinglayer 41 has its outer peripheral surface provided with a plurality ofpositioning ridges 42, and the metal layer 43 has its inner peripheralsurface formed with a toothed channel 44. When assembled to thetransmission shaft 27, the bushing 40 is inserted into the inner shafthousing 33 so that its rear end abuts against the retaining flange 35 ofthe inner shaft housing 33. The bushing 40 on one hand uses the fourpositioning ridges 42 on the shock-absorbing layer 41 to pair up andengage with the four positioning recesses 36 of the inner shaft housing33, and on the other hand uses the toothed channel 44 of the metal layer43 to engage with the toothed portion 28 of the transmission shaft 27.Then two gaskets 46 are arranged at front and rear ends of the impellershaft 31 for the transmission shaft 27 to pass. At last, a nut 47 isassembled to hold all the components together, thereby making theimpeller 30 and the transmission shaft 27 well assembled. As a result,the transmission shaft 27 of the gear box 20 can transmit powergenerated by the engine to the impeller 30 through the bushing 40,thereby driving the impeller 30 to operate. In the event that a foreignobject comes to the impeller 30 during operation, the shock-absorbinglayer 41 serves to absorb impact and to prevent the metal layer 43 fromburst while protecting the transmission shaft 27 from damage. Moreover,in the assembly of the impeller 30 and the transmission shaft 27, thereis no direct contact between the impeller shaft 31 and the tapered shaft22 of the casing 21. Instead, an exhaust channel 45 is left therebetween to allow escape of exhaust gas (as shown in FIG. 6).

At the top edge of the outer peripheral surface of the stream-guidingring 50, two upper supports 51 are symmetrically fixed using fixingmembers 53 such as screws. The upper supports 51 jointly hold theanti-swirl baffle 26 in position and then the upper supports 51 can befurther fixed using fixing members 54 such as screws. At the bottom edgeof the outer peripheral surface of the stream-guiding ring 50, a lowersupport 52 is fixed using fixing members 55 such as screws. The lowersupport 52 holds the lower wing 24 in position and the lower wing 24 canbe further fixed using fixing members 56 such as screws. After soassembled, the stream-guiding ring 50 houses the entire impeller 30.

As shown in FIG. 2 and FIG. 5, the stream-shaping nozzle 60 has a ringportion 61, a hollow axial portion 62, and eight stream-shaping portions63. The ring portion 61 is fixed to the rear end of the stream-guidingring 50 using fixing members 64 such as screws. The ring portion 61 hasa changing cross-sectional area that becomes smaller as it extendsbackward. The hollow axial portion 62 is defined in the ring portion 61.The hollow axial portion 62 has its front end provided with an engagingsocket 65. The engaging socket 65 of the hollow axial portion 62coaxially receives the engaging flange 34 of the impeller shaft 31 ofthe impeller 30 (as shown in FIG. 6). The stream-shaping portions 63 areintegratedly connected between the ring portion 61 and the hollow axialportion 62 while being arranged equidistantly to circle the hollow axialportion 62. Thereby, water streams drawn into the stream-guiding ring 50by the impeller 30 are well shaped into eight linear streams by theeight stream-shaping portions 63 of the stream-shaping nozzle 60. Thenthe stream-shaping nozzle 60 jets the linear streams backward to providethe boat with propulsion.

With such a design, the boat propeller 10 of the present invention hasthe following advantageous over the prior-art devices:

1) Given that the stream-guiding ring 50 is attached to the casing 21 ofthe gear box 20 through the upper and lower supports 51, 52 and that theimpeller shaft 31 of the impeller 30 is not tapered, the diameter of thecombined vanes 38 is enlarged and so is the water volume to becompressed. As a result, the effective water inlet diameter is maximizedto provide improved propulsive efficiency.

2) With the protection provided by the stream-guiding ring 50, theimpeller 30 is unlikely to harm fishes, swimmers or divers around tobottom of the boat. This allows a boat having a shallow draft safe to beused. Even if the impeller 30 is not fully immersed in water, propulsioncan still be provided desirably. Besides, the stream-guiding ring 50 maybe made of aluminum alloy which is of high strength. In this case, theboat propeller 10 is more resident to impact and has a longer servicelife.

3) When the boat moves backward, the exhaust gas generated by the enginecan escape through the exhaust channel 45 and will not interfere withwater streams and cause turbulence.

4) The stream-shaping nozzle 60 uses the eight stream-shaping portions63 to shape the water stream excited by the impeller 30 into linearejections. This prevents swirls from formed at the back of the impeller30 and in turn helps to improve propulsive efficiency.

5) The transmission shaft 27 of the gear box 20 and the impeller shaft31 of the impeller 30 are assembled coaxially, so that the power of theengine can be leveraged, while the bushing 40 works as a buffer againstexternal impacting force.

What is claimed is:
 1. A boat propeller, comprising: a gear box,including a casing and a transmission shaft, wherein the transmissionshaft is rotatably installed in the casing and has a front end thereofsuch received in the casing that a rear end thereof juts out the casing;an impeller, including an impeller shaft and a plurality of vanes,wherein the impeller shaft has a hollow columnar outer shaft, a hollowcolumnar inner shaft housing, and a plurality of rib portions, in whichthe inner shaft housing is received in the outer shaft housing andcoaxially connected to the transmission shaft of the gear box, and therib portions are connected between the outer shaft housing and the innershaft housing, while the vanes are integratedly connected to an outerperipheral surface of the outer shaft housing of the impeller shaft; astream-guiding ring, which is assembled to the casing of the gear boxand houses the impeller; and a stream-shaping nozzle, which is connectedto a rear end of the stream-guiding ring.
 2. The boat propeller of claim1, wherein the stream-shaping nozzle has a ring portion, a hollow axialportion, and a plurality of stream-shaping portions, in which the ringportion is connected to the rear end of the stream-guiding ring, and thehollow axial portion is defined in the ring portion and coaxiallyconnected to the outer shaft housing of the impeller shaft of theimpeller, while the stream-shaping portions are connected between thering portion and the hollow axial portion and arranged equidistantly tocircle the hollow axial portion.
 3. The boat propeller of claim 2,wherein the ring portion of the stream-shaping nozzle has a changingcross-sectional area that becomes smaller as the ring portion extendsaway from the stream-guiding ring.
 4. The boat propeller of claim 1,wherein the casing of the gear box has a tapered shaft, and an exhaustchannel is formed between the tapered shaft and the impeller shaft ofthe impeller.
 5. The boat propeller of claim 4, wherein the casing ofthe gear box further has an upper wing, a lower wing, and an anti-swirlbaffle, in which the upper wing and the lower wing are integratedlyconnected to top and bottom sides of the tapered shaft, and theanti-swirl baffle is integratedly connected to the upper wing so it islocated above the stream-guiding ring; two upper supports beingsymmetrically fixed to a top edge of the outer peripheral surface of thestream-guiding ring for connecting the anti-swirl baffle, and a lowersupport being fixed to a bottom edge of the outer peripheral surface ofthe stream-guiding ring for connecting the lower wing.
 6. The boatpropeller of claim 5, wherein the casing of the gear box further has aconnecting portion that is integratedly connected to a top of the upperwing so as to be located above the anti-swirl baffle.
 7. The boatpropeller of claim 1, wherein the inner shaft housing of the impeller isindirectly connected to the transmission shaft of the gear box through abushing.
 8. The boat propeller of claim 7, wherein the inner shafthousing has an inner peripheral surface thereof provided with apositioning recess, and the bushing has an outer peripheral surfacethereof provided with a positioning ridge, so that the positioning ridgeof the bushing engages with the positioning recess of the inner shafthousing.
 9. The boat propeller of claim 8, wherein the bushing has ashock-absorbing layer and a metal layer wrapping the shock-absorbinglayer, in which the shock-absorbing layer has an outer peripheralsurface thereof provided with the positioning ridge, and the metal layeris connected to the transmission shaft.